Problem: Simplify the following expression: $t = \dfrac{1}{2z} - \dfrac{5}{3z}$
In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $2z$ and $3z$ $\lcm(2z, 3z) = 6z$ $ t = \dfrac{3}{3} \cdot \dfrac{1}{2z} - \dfrac{2}{2} \cdot \dfrac{5}{3z} $ $t = \dfrac{3}{6z} - \dfrac{10}{6z}$ $t = \dfrac{3 -10}{6z}$ $t = \dfrac{-7}{6z}$